The invention relates to a flexible implant for the stabilization of bones or vertebrae, wherein the implant is formed as a solid body that has at least one cavity located near the surface wherein the cavity is connected to the surface through at least one slit and wherein a width of the slit is smaller than a width of the cavity. The slit is configured to narrow when the implant is flexed, and the closing of the slit during flexion limits the extent of flexion of the implant. The implant may be realized, for example, as a bone screw, a stabilization rod, or a bone plate.
Dynamic stabilization devices are known, in which the bone parts or vertebrae to be stabilized are able to carry out a controlled limited motion relative to each other. For example, a rod-shaped implant for the connection of bone anchoring elements that includes at least one rigid section that is configured to be placed in a receiver member of a bone anchoring element and a flexible section that is adjacent to the rigid section and wherein the flexible section and the rigid section are formed as a continuous one-piece element is known from U.S. Pat. No. 7,621,912 B2.
An elastic or flexible element for use in a stabilization device for bones or vertebrae in the form of a helical spring is known from US 2005/0154390 A1. The flexible element can be part of the shaft of a flexible bone screw or of a stabilization rod or a plate.
Such known flexible implants include a longitudinal bore and a helical slot-shaped opening in the wall. The flexibility is determined by the geometry of the hollow bore and the helical slot-shaped opening. To limit the flexibility or strengthen the implant, a core may be provided in the hollow bore. The flexible characteristics of the known devices can be precisely designed by the geometry of the helical slot-shaped opening and the dimensions of the hollow bore and optionally the core inserted therein. However, such implants sometimes do not have a limitation of the flexibility, or a limitation of the flexibility to a certain degree requires a more complex design in terms of the number of parts or the materials used. Therefore, there remains a need for a further improved flexible implant.